The present invention relates to plasma etching. More particularly, the present invention relates to a method for scaling processes between different plasma etch chambers as well as different wafer sizes.
Reactive ion etching and plasma etching are commonly used in the industry. A plasma having specific properties will yield a specific process result on a wafer. In order to obtain the desired process result, the characteristics of the plasma must be identified and controlled. A plasma is generally characterized by its properties (e.g. electron temperature, ion density, neutral density, etc). These plasma properties are generally controlled by process xe2x80x9cknobsxe2x80x9d, such as RF power, chamber pressure, gas flow, etc. However, the effects of these process knobs may vary depending on the specific geometry of the each chamber and the size of each wafer.
Current process transfer between different generations and classes of etch chambers rely on running large design of experiments (DOEs) in each chamber and comparing process results. The next step of the process transfer would match the process results and compare the process windows of each chamber. This qualitative matching would then result in a process transfer between the etch chambers. Typically, a xe2x80x9cprocess matchxe2x80x9d is qualitative in nature because the process results such as etch rate, selectivity, etc do not all match together, but are close enough for the user""s specific application. Therefore, many wafers are processed and discarded in order to match the process results.
In a true process transfer, the important etch parameters such as electron temperature, ion density, neutral density, ion energy, residence time, etc. would be matched in each chamber. Once the plasma properties are matched, the process results should also match. Unfortunately, with the current methodology, there is no assurance that this occurs.
The difficulty in determining scaling factors arises from the coupled nature of plasma. Changing one process knob usually affects many plasma characteristics. For example, changing the pressure will not only change the electron temperature but also the ion density, the residence time, and other parameters.
Accordingly, a need arises for a quantitative method for scaling processes between different etching chambers and wafer sizes, to match the important etching parameters in each chamber.
A method scales plasma process settings from a first processing device to a second processing device. The first processing device has a first geometry and a first set of process parameters. The second processing device has a second geometry and a second set of process parameters. A first set of plasma process settings that generates the first set of process parameters of the first processing device having the first geometry is determined. The first set of plasma process settings is reduced to isolate at least one variable on which the first set of plasma process settings depends on for each plasma process setting. A scaling factor is calculated for each plasma process setting from the first set of plasma process settings such that the first set of process parameters substantially equals the second set of process parameters. A second set of process settings is determined for the second processing device having the second geometry by multiplying each scaling factor with each plasma process setting from the first processing device having the first geometry.